Pedal assemblies for controlling clutches often use an over-the-center spring mechanism to generate an initial force which resists the activation of the pedal. Once the pedal passes over the center of the mechanism, the spring assists somewhat in activating the pedal.
The problem with this solution is that the shape of the force vs. stroke profile is generally constrained. In some applications, the force vs. stroke profile cannot be adequately provided by an over-the-center spring mechanism.
A more robust solution is desired. In particular, it would be especially useful to tailor the force vs. stroke profile to the needs of any particular application.